In recent years, ink-jet recording methods have found wide application in the field of various kinds of graphic arts such as photography, various kinds of printing, marking and specific printing such as color filters due to its ability to form images simply and cheaply. Particularly, it has also become possible to obtain image quality comparable with silver salt photography by utilizing a recording apparatus which ejects and controls minute dots; ink in which color reproduction range, durability and ejection suitability have been improved; and exclusive paper in which ink absorption, color forming property of the colorant and surface gloss have been greatly enhanced. Image quality improvement of current ink-jet recording methods has been achieved only when complete set of a recording apparatus, ink and exclusive paper are employed as a system.
However, an ink-jet system which requires exclusive paper is problematic with respect to limitations of recording media and increased cost of such recording media. Therefore, many attempts have been made to record on a medium, on which ink is to be transferred, differing from exclusive paper by means of ink-jet recording. Specifically, there are phase-conversion ink-jet methods utilizing wax which is solid at room temperature, solvent-type ink-jet methods utilizing an ink which is comprised mainly of a rapid-drying organic solvent, and UV ink-jet methods in which an ink is cross-linked by ultraviolet (UV) light after recording.
Among these, the UV ink-jet methods have been noted recently due to relatively low odor compared to solvent-type ink-jet methods, rapid drying of prints and the capability of recording on a recording medium without ink absorption property; UV-curable ink-jet inks are disclosed (for example, in Patent Documents 1–3).
However, even when these inks are employed, ink dot diameter after deposition may change greatly depending on the kinds of recording medium and working environment, leading to difficulty to form high definition images onto all the kinds of recording media.
On the other hand, as ink-jet recording methods ejecting inks using ink-jet recording heads, well known are a piezo method, a thermal method and a continuous method. Of these, the piezo method using piezoelectric members is widely employed from the viewpoint of ejecting stability. Said piezo method is a method which ejects ink droplets from ink nozzles by changing pressure in ink chambers using actuators such as piezoelectric members which function by deformation actuation based on applied voltages. In general ink-jet Recording Heads, many ink chambers and ink nozzles are provided from the viewpoint of forming high image quality and high-definition images. However, this causes problems such as “cross talk”, which means that change of pressure in ink chambers during image formation causes fluctuation in adjacent inks. As a result, accuracy of ink droplet flight decreases to result in hindrance to formation of high-definition images. Specifically, compared to water base ink, it has been proved that this phenomenon is notably observed on the above-mentioned UV curable ink having high viscosity in ink droplets.
As one of the methods to solve the above cross talk, the following improving method is proposed (for example, refer to Patent Document 4). That is, to provide a predetermined quiescent time between an expansion pulse which functions to expand volumes of ink chambers by deformation actuation of actuators comprising ink chamber dividing walls, and a shrinkage pulse which functions to compress volumes of ink chambers by deformation actuation of actuators, to provide a continuous driving signal generation means for multiple times generating driving signals applied to the actuators, to continuously eject plural ink droplets from ink ejecting orifices by repeated expansion and compression of ink chamber volumes during multiple times of the driving signals from a driving signal generation means, and accompanying the above to set up the quiescent time to decrease the cross talk among the ink chambers adjacent to each other. However, in the above invention, there is no description about the characteristics of the ink used.
Further, ink employed in the traditional UV curable ink-jet method has drawbacks, that is, recording media tend to easily shrink with that ink. Specifically, thin plastic films used for flexible packaging, such as food packaging, and pressure sensitive adhesive labels tend to result in shrinkage. As a result, in flexible packaging printing and label printing, the UV curable ink-jet method has not yet been practical in use in the cited situations.
Patent Document 1: Examined Japanese Patent Publication 5-54667
Patent Document 2: Unexamined Japanese Patent Publication 6-200204
Patent Document 2: Japanese Translated PCT Patent Publication 2000-504778
Patent Document 4: Unexamined Japanese Patent Publication 2000-19103 (Claims)